Another application for two degree of freedom manipulators is in the use of rehabilitation robots in order to provide support and/or assistive forces to a patient undergoing rehabilitation. Such manipulators are attached to a body part of the subject and can be used to provide assistive forces and support during a rehabilitation exercise such as gait training.
For example, a 2DOF manipulator may be connected to a subject's pelvis to support their weight and provide predetermined gait cues to assist in walking One such manipulator is shown in US2007/0016116. In this document, a pair of pneumatically driven manipulators apply forces to the subject's pelvis with an arrangement of cylinders. In particular, fore-aft movement of the subject is provided by pneumatic cylinders mounted in the fore-aft direction, and lateral movement is provided by laterally orientated pneumatic cylinders. A problem with this arrangement is that the lateral cylinders mean that the manipulator is quite wide. This makes it more difficult to install, and the laterally extending pneumatic cylinders may clash with the subject's arms during normal gait motion. Also, the workspace is quite small compared to the size of the manipulator.
A different, known, 2DOF manipulator comprises a 2D Cartesian slideway arrangement in which a carriage is slidable on a first rail in a first direction, which first rail is slideable between two further parallel rails in a second direction, perpendicular to the first. Such systems have certain disadvantages.
One disadvantage is that there is a significant amount of equipment surrounding and within the workspace. This is generally undesirable in many applications, as the manipulator and the workpiece or subject may clash, and in the event that the manipulator is used for gait training, the rails may clash with the subject's arms.
Another disadvantage with such systems is that sliding joints between components are generally undesirable because they are prone to contamination and wear.
Also, in such a system a motor is provided to move the carriage on the first rail. The provision of a motor attached to the first rail, and arranged to move the carriage, means that the first rail has a high inertia, which is undesirable when being moved on the parallel rails.